This introduces and reworks some utility functions for retrieving or

parsing information on apps. get_app_label() and get_app_name() now

retrieve their informatoin from the AppConfig on Django 1.7+, and the

AppConfig can now be retrieved through get_app_config_for_app(). The

old legacy version of the label can be returned using

get_legacy_app_label().
At the moment, this will return some incompatible information for apps

when using a new-style app label on modern versions of Django, but this

wasn't expected to work yet anyway.
Model fetching also has fixes on Django 1.7+. It no longer assumes

anything about the provided app module's label, and instead loops

through apps looking for one that owns the provided module.
These will be needed for the app label support coming in the next

change.

Unit tests pass on Django 1.6. This change temporarily breaks them on

newer versions.